The present invention relates to a particular warp size composition for the application to certain yarns of blends of synthetic and natural fibers or wholly of natural or synthetic fibers to improve the overall performance, economics, and handling of same during fabric formation.
It is necessary to apply a warp size composition to textile strands or yarns to permit handling of the materials during fabric formation operations, normally weaving, to preclude damage to the yarns during such operations. In general, from commercial and operational standpoints, size compositions that are applied to the yarns must meet certain criteria for successful use in performance of the intended purposes. For example, irrespective of the yarn materials utilized in fabric formation, the size must adhere thereto throughout the operation to protect the fibers from abrasion due to contact with process equipment or adjacent fibers, and thereafter must be easily removable from the formed fabric to permit further finishing and processing of the fabric.
During the evolution of synthetic polymeric filamentary materials, and spun yarns produced therefrom, it became evident that the general types of sizing compositions historically utilized for application to natural fibrous materials were not satisfactory. Particularly, the synthetic polymeric materials are hydrophobic in nature whereas the natural fibrous materials are hydrophilic in nature. Hence different materials were needed that would properly adhere to the synthetic polymeric yarns.
Natural, or generally hydrophilic fibers such as cotton, linen, rayon and the like may be sized with various forms of starch, such as hydrolyzed starches, dextrins, partially esterified starches,and partially etherified starches. Additionally, water soluble carboxymethyl cellulose, water-soluble hydroxyethyl cellulose, natural gums such as guar, gum arabic, sodium alginate and the like may also be used. The above noted sizing agents for natural fibers are generally film formers, and are not in general suitable for use, per se, on synthetic, polymeric fibers such as nylon, polyester, polyacrylonitrile, and cellulose acetate, and likewise on glass fibers. Particularly, aqueous dispersions or solutions of only the above referred to size agents will not adhere to the synthetic, or glass fibers or filaments to afford the protection necessary during fabric formation.
It has been previously determined that certain polymeric sizing agents which are either water dispersible, water soluble, or soluble in dilute alkaline solutions may be suitably employed to size the hydrophobic, synthetic polymeric fibers and filaments. Exemplary of such polymeric sizing agents, without limitation, include polyacrylic acid, polymers of acrylonitrile, polymers of lower alkyl acrylates, maleic anhydride copolymers, polyvinyl alcohol, polyesters and the like.
Depending upon the chemical structure of the polymeric sizing agent, the agent may be suitable for application to both synthetic filamentary materials and spun yarns that contain synthetic fibrous materials. Certain functional groups, if present, on the polymeric size, may render same unsuitable for spun yarns. For example, if during the processing of same, the size is cross linked or otherwise reacted with the synthetic fibrous material in the blend, easy removability of the size is hindered, if not totally negated.
Today's textile market finds the natural fibers appreciably more expensive than the manmade fibers, whereby blends of the two have been utilized successfully for many fabric end uses. Moreover, the manmade or synethetic fibers possess certain qualities that render yarns or blends containing same desirable due to improved physical properties. A single strand of spun yarn constituted by a blend as mentioned hereinbefore has both hydrophilic and hydrophobic characteristics, and accordingly, in order to apply a size composition thereto that is adequately adherent to both types of fiber constituents, it has generally been accepted that blends of size constituents such as those set forth above should be utilized.
Polyester resins suitable for use in warp size compositions for spun yarns that include synthetic fibers in general, due to the chemical composition of same, are generally adhesive at ambient conditions such that agglomeration of particles of resin occurs, even due to cold flow. Consequently polyester-starch or other textile size compositions utilizing a polyester resin have heretofore been blended at the time of preparation of the aqueous dispersion just prior to use, or prepared and shipped as an aqueous dispersion.
Generally the formation of an aqueous dispersion of a blend of size ingredients whether for spun blends or otherwise is accomplished by mixing the ingredients according to a particular recipe in a cooking vessel along with the dispersing medium, generally water, and bringing the mixture to a desired consistency for application to the yarn. Since formulation is generally conducted just before application, and thus may occur at any hour of the day, potential problems exist with maintenance of uniformity of ultimate size compositions, particularly since unskilled laborers are often involved.
To some extent, attempts have been made to circumvent the above noted problems. A particular example of such an attempt is a size composition referred to in the Lark U.S. Pat. No. 3,981,833 which is directed to a warp size composition that includes starch or some other size ingredient suitable for adhesion to the hydrophilic yarns and a polyester resin suitable for adherence to polyester yarns. The Lark composition is generally directed to a pasted starch blended with a polyester resin. Pasted starch of course refers to an aqueous starch composition which is later blended with the polyester resin at the consumer's location, or alternatively, the two may be preblended, and the aqueous blend shipped to the consumer. Lark thus appears to perhaps reduce problems attendant with formulating the size composition at the time of use, but does not overcome same.
Under all known prior art conditions, the consumer either relied upon unskilled labor in preparation of the size composition, or was required to purchase the preblended aqueous dispersion which included the cost of preblending and shipping the water. The present invention provides a dry, premixed, size composition which alleviates the aforementioned agglomeration or cold flow problems of the polyester constituent; affords ease of bulk handling and package compatibility of ingredients; is economical to transport; is provided to the consumer in a form that eliminates mixing errors, and further attributes improvement in weaving performance of the spun yarns sized therewith. According to the present invention, the polyester resin is provided in particulate form in such a manner that agglomeration is precluded, whereby a proper complete blend of size ingredients may be supplied to the consumer which can then be easily and conveniently dispersed in an aqueous medium as desired.
Polyester resins in general have heretofore been provided in particulate form for certain purposes, e.g., for the formation of casting or molding resins. The Chetakian et al U.S. Pat. No. 3,027,338 is directed to a polyester molding composition that is fiber reinforced. The polyester constituent of the molding composition, in crystalline form, is ground at a low temperature, below the melting point of the resin after which the molding composition is produced. In similar fashion, Cruz et al U.S. Pat. No. 3,931,082, relates to colloidally dispersible microcrystalline polyesters which are hydrolyticly treated to remove amorphous regions after which the polyester is mechanically disintegrated by various techniques, one of which is freeze grinding. Neither Chetakian nor Cruz, Jr., et al, however, in any way relate to a warp size composition for textile materials, and in fact, the polyesters of same are unsaturated and would thus not be suitable for use as textile size ingredients.
U.S. Pat. Nos. 3,546,008 to Shields et al and 4,150,946 to Neel both disclose polyesters suitable for use as textile size compositions and that the resin may be provided in pellet, powder or flake form at the time of preparation of the aqueous dispersion of same. The Shields et al and Neel polyesters, however, are intended for use as polymeric sizes for synthetic filaments and are not suitable in their present form for use as size ingredients according to the present invention since during processing of the yarns with a conventional alkali scour, the polyester size of Shields or Neel would become affixed to the synthetic fibers and could not be easily removed.
The present invention thus affords numerous advantages over prior art warp size compositions for fibrous yarns of synthetic and/or natural fibrous materials as set forth above, and known prior art is not believed to anticipate or suggest same.